Ashlee and Erik Dahlberg of Lowell, Indiana, lost their 8-year-old son, Liam, to a vaccine-preventable disease in April.

“I thought having the vaccines would protect our children,” Erik Dahlberg said. “Unfortunately, it did not because other kids, other adults, need to be vaccinated as well in order for it to work.”

Liam was particularly vulnerable because he had severe asthma and allergies. He was vaccinated against Haemophilus influenzae type b, or Hib, but it caused his brain to swell and killed him less than two days after he complained of a headache. Hib is transmitted by respiratory droplets, often spread by coughs and sneezes. Doctors said Liam’s case likely stemmed from someone unvaccinated, Ashlee Dahlberg said.

With two other children, the Dahlbergs worry about living in one of the many U.S. communities with low immunization rates. State statistics show one in five kindergartners in their county don’t meet vaccination requirements.

“There’s no pain that is worse than the pain of losing a child,” said Ashlee Dahlberg, who brings an urn with Liam’s ashes on family camping trips so he won’t be left out.

The Dahlbergs and others are fighting a strong anti-science movement that stresses “health freedom” but disputes proven health measures. Experts say global vaccine efforts have saved more than 150 million lives since 1974.

An Associated Press investigation found more than 420 anti-science bills attacking longstanding public health protections – vaccines, milk safety and fluoride – have been introduced in statehouses across the U.S. this year, part of an organized, politically savvy campaign to enshrine a conspiracy theory-driven agenda into law.

The wave of legislation has cropped up in most states, pushed by people with close ties to Health and Human Services Secretary Robert F. Kennedy Jr. The effort would strip away protections that have been built over a century and are integral to American lives and society. Around 30 bills have been enacted or adopted in 12 states.

Trump administration officials are directing activists to push anti-science legislation in the states – where public health authority rests – with the ultimate goal of changing laws and minds nationally.

The effort normalizes ideas fueled by the anti-vaccine movement that Kennedy has helped lead for years. His Make America Healthy Again agenda masks anti-science ideas while promoting goals such as making food more natural or reducing chemicals. Meanwhile, vaccination rates continue to fall, allowing the infectious diseases measles and whooping cough to make comebacks as Kennedy has sought to broadly remake federal policies on public health matters including fluoride and vaccines.

Kennedy’s allies dispute that their agenda is anti-science or driven by conspiracy theories, but many experts disagree.

In its analysis of legislation, AP focused on public health policies which have clear medical evidence behind them and are targets of the Make America Healthy Again movement. AP searched 2025 legislation in all 50 states, analyzing more than 1,000 bills collected by the National Conference of State Legislatures and the bill-tracking software Plural for whether they undermined science-based protections for human health.

Anti-vaccine bills – 350 of them – were by far the most common. They come at the issue from various angles: barring discrimination against unvaccinated people, creating the criminal offense of vaccine harm, requiring blood banks to test for evidence of vaccinations and instituting a 48-hour vaccine waiting period.

Legislators acknowledge they sometimes draw inspiration from other states: Bills in numerous places target mRNA vaccines, which were credited with saving millions of lives during the pandemic.

Most bills haven’t passed – some died and others are pending – but at least 24 anti-vaccine laws have been adopted in 11 states this year.

Most of those bills were supported by at least one of four national groups connected to Kennedy: MAHA Action, Stand for Health Freedom, the National Vaccine Information Center and the Weston A. Price Foundation.

The groups also opposed dozens of science-driven bills, including one that would protect people by tightening rabies vaccine requirements for pets.

Lawmakers fighting for science-based policies say what’s missing in the discussion is concern for the public good.

Rep. Andy Vargas, a Massachusetts Democrat, has been sponsoring legislation since 2019 to eliminate religious exemptions from childhood vaccines. Despite high vaccination rates in Massachusetts, Vargas said, pockets in every county have lost herd immunity for measles.

In Indiana, Democratic State Rep. Maureen Bauer, of South Bend, said these issues are often falsely framed as parents’ rights and individual freedom.

Though there’s no way to know for sure who exposed Liam Dahlberg, research shows unvaccinated people are more likely to carry Hib and spread it. Severe cases dropped by over 99% after the federal government recommended the vaccine in 1991.

In recent years, however, overall vaccination rates have dropped.

After Liam died, the Dahlbergs learned that vaccine policies vary by state. Hib shots are recommended, not required, to enter pre-kindergarten in Indiana, though they are required in Illinois, a 10-minute drive from home. These states and nearly every other allow parents to opt their children out of vaccine mandates for non-medical reasons such as religion.

Ashlee Dahlberg channeled her anger into purpose, starting a change.org petition to eliminate religious exemptions in public schoools nationally. While most feedback has been positive, she said, they’ve received hateful messages, including: “Your son deserved to die.”

But, Dahlberg said, “I want to reach those parents who are on the fencepost about vaccinations.”

The Dahlbergs feel it’s up to them to protect their two surviving children from vaccine-preventable diseases. They can’t rely on their government anymore.

They’ve considered homeschooling 6-year-old Ava and 11-year-old Khloe. For now, they’ve made arrangements with Ava’s school to ensure every student in her class is vaccinated. Like her brother, she has severe asthma. In common areas such as hallways or buses, she wears a mask.

On the first day of school this year, Dahlberg called Ava to the kitchen to take puffs from her twice-a-day inhaler before ushering the girls outside for first-day pictures. They walked past the collection of mementos reminding them of Liam – his handprint, a photo of him with his dirt bike, a plaster cast of his hand in his mom’s. The girls held a photo of their brother as they stood near a flowering crab apple tree planted in his memory.

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The Associated Press Health and Science Department receives support from the Howard Hughes Medical Institute’s Department of Science Education and the Robert Wood Johnson Foundation. The AP is solely responsible for all content.